1. Field of the Invention
The present invention relates to an exposure apparatus for manufacturing a device such as a semiconductor device or a liquid crystal device, and more particularly, to an exposure apparatus configured to expose a substrate to radiant energy with an original plate (also referred to as reticle or mask) and the substrate scanned in a scanning direction traversing an optical axis of a projection optical system.
2. Description of the Related Art
In transferring a circuit pattern onto a wafer, a reticle having an integrated circuit pattern is illuminated with light emitted from an optical system and the illuminated pattern is projected onto the wafer by a projection optical system. During this process, it is necessary to adjust a focus of the projection optical system so that the pattern on the reticle is formed on the wafer with precision.
However, depending on a pattern formed on the wafer, the focus may not be correctly measured at the exposure position. In such a case, if the apparatus is a one-shot exposure type stepper, a focus on a substrate position different from an exposure position is measured before the exposure. This technique is called “shift focus”. However, regarding a scanning exposure type scanner, since a focus measurement and exposure of the substrate are performed while the substrate is being scanned, a shift focus method similar to that for the stepper is not utilized.
Thus, in a conventional technique, it is possible that a measurement point overlays a scribe line and proper measurement cannot be performed. Further, as a special case, if the wafer includes a test element group (TEG), which is commonly formed on the wafer together with the chip, its exposure area may be set at an X position considerably distant from a line that goes through the center of the reticle in the scanning direction (Y direction) (see FIG. 8A) or its exposure area having a short Y width may be set at a position shifted in the Y direction from the center of the reticle (see FIG. 8B). In these cases, the focus is adjusted based on focus measurement information of a shot area near the shot area for the exposure. However, in some cases, the focus is not precisely adjusted based on the focus measurement information.